The invention relates to detection of neutrons by a moderating, position sensing detection system. The system discriminates neutrons from gamma rays via pulse height analysis. By detecting the absorption position of a neutron along the detection element, neutron spectroscopic data can be collected. The system maintains a flat response over a wide range of incident neutron energies.
Various methods of measuring neutron energies have been employed based on moderation of fast neutrons. These detection schemes involve the placement of thermal neutron detectors within a moderating medium. Early experiments used a large water bath as the moderator. Count rates obtained at different depths were used to provide crude spectroscopic data. More recently, a rudimentary neutron spectrometer was developed using a lithium iodide scintillator placed at the center of polyethylene moderating spheres of different diameters (Bonner spheres). Information regarding neutron energy of an unknown source was acquired by measuring count rates obtained with each of the moderating spheres and comparing these results to calibration curves. The deconvolution process, as well as the redundant experimental procedures required, makes these spectrometers cumbersome, limiting their use.
A neutron spectrometer based on total energy absorption in a liquid scintillator moderator and a coincident capture by .sup.6 Li-loaded glass plates immersed in the liquid is disclosed in U.S. Pat. No. 4,931,649 issued on Jun. 5, 1990 to Czirr and Jenson. A complicated signal processing system is required to perform the various tasks of coincident analyses, pulse-shape discrimination, and pulse-height analysis.